The present invention relates to glasses which have the capacity of scintillating when subjected to nuclear, neutron or gamma radiation.
Scintillators are finding ever increasing applications in nuclear physics, particularly for the purposes of detecting and/or identifying high speed particles. The material through which the high speed particles travel is stimulated. This causes the kinetic energy of the particles to be stepwise transmitted to the molecules of the material. It is then emitted in the form of light.
In addition to ZnS or NaI crystals, glass may also be used as a scintillation material or scintillation counter. Moreover, it has the special advantage that it can be produced substantially more cheaply and in any conceivable form and size. Glasses of this type have been known for some time, for example from GB-PS 869,055, U.S. Pat. Nos. 3,052,637, 3,097,172, GP-PS 905,391, U.S. Pat. No. 3,032,428, SU-PS 565,893, JP-OS 44-14 826, JP-OS 52-957 15, JP-OS 52-957 15, JP-OS 52-30289 and JP-OS 81-05344.
However, SU-PS 565,893 describes a radio-thermoluminescent material, i.e., not a scintillation counter in the narrower sense of the definition. The two Japanese patent applications Nos. 52-95 715 and 52-30289 describe Cerenkov-glasses, i.e., materials likewise designed for proving the presence of fast particles, but by virtue of a different method (Cerenkov-effect). Japanese OS 44-14826 describes a low-fluorescent glass for a container which may be filled with a scintillating fluid; in other words, it is not itself a scintillation counter. GB-PS 905,391 describes a combination of scintillating material as a thin coating on a scintillation-free basic glass.
Glasses which are used for genuine scintillation-measuring operations are also known, e.g.:
(a) a high-SiO.sub.2 -containing glass with Ce.sub.2 O.sub.3 -contents in excess of 3% by weight produced by leaching out a phase-separated borosilicate glass using sugar as a reducing agent (GB-PS 869,055);
(b) a lithium-aluminum-silicate glass with 0.3 to 2% by weight of Ce.sub.2 O.sub.3 produced in a reducing smelting process with carbon (U.S. Pat. No. 3,097,172);
(c) an alkali-aluminum-borate-glass with Ce added in the form of cerium oxalate as a reducing agent (U.S. Pat. No. 3,052,637);
(d) an alkali-aluminum-borate-glass with cerium oxide smelted in a reducing atmosphere (U.S. Pat. No. 3,032,428); and
(e) an alkaline-earth silicate-glass with cerium oxide smelted under reducing conditions (JP-OS 81 05 344).
These glasses display the scintillation effect very well but they have the disadvantage that the ratio of cerium (IV) to cerium (III) which is required for scintillation is obtained by a reduction of the melt.
Such a reduction, whether obtained by means of oxalates, sugar or carbon, or by means of a reducing atmosphere, e.g., a forming gas, however, has a very serious drawback. Such glasses cannot be produced in noble-metal-smelting vessels because the metal, or precious metal alloy, corrodes. The alternative adoption of quartz- or ceramic crucibles, on the other hand, critically lowers production capability because smelting in a quartz crucible causes the material to dissolve, i.e., causes the formation of bubbles and schlieren in the production of larger castings.